A Holter monitor, comprising electrodes placed on a patient's chest area and attached to a recorder carried externally by the patient, provides a continuous electrocardiograph (EKG) of heart rhythm for a pre-determined period, for example, 24 hours. Certain precautions must be observed. For example, the electrodes must not be touched, adjusted or subjected to moisture. The externally worn Holter monitor with the attached skin electrodes tends to be both inconvenient and uncomfortable.
The Medtronic Reveal® insertible loop recorder is an attempt to overcome some of the disadvantages of the Holter monitor. The Medtronic recorder is a subcutaneously implantable device having a pair of spaced-apart sense electrodes for detecting cardiac far field electrograms. However, the device is relatively bulky and its subcutaneous implantation necessitates significant surgery.
Implantable, microminiature, radio-telemetrically operated sensors injectable through the lumen of a hypodermic-type needle have been developed for small animal research. These sensors receive their power wirelessly from an external power source via a radio frequency magnetic field inductively coupling a coil on the external power source with a coil within the implant. Accordingly, the animal must be maintained in close proximity to the external power source.
There continues to be a need for a minimally invasive cardiac event recorder that is easily implantable in a human body, is completely self-contained and automatically senses and records cardiac events for subsequent retrieval and analysis with minimum discomfort and inconvenience to the patient.